1. Field of the Invention
The present invention relates in general to a new and improved uninterruptible power supply apparatus. More particularly, it relates to a new and improved dc to ac inverter portion in said uninterruptible power supply.
2. Description of the Prior Art
Various backup, standby or emergency power systems have been known and used in the past. These prior art units were used to supply power in various areas when the commercial ac power supplied by the utility company was interrupted momentarily or was cut off for a greater length of time. Some of these prior art systems require a certain length of transfer time when they were required to supply the needed power in the emergency. These systems would sense the failure of the commercial ac power and would then transfer the emergency power system to take the place of the commercial ac power. The transfer or substitution of the backup system could result in a discontinuity in the supply of ac power. This transfer time and discontinuity of available ac power was not detrimental in the majority of applications.
With the advent of the computer and microprocessor-based equipment together with the programs and data associated therewith, it was necessary to provide continuous and uninterrupted power to such equipment. The transfer time, discontinuity and power anomalies associated with supplying power to computer and microprocessor-based equipment could no longer be tolerated because of the possible time and money which could be lost with the loss of data, damage to equipment, etc.
The present invention provides an uninterruptible power supply which eliminates many of the prior art deficiencies in systems which are the forward transfer or standby systems. Many prior art systems have complicated electronic systems which render the systems expensive and of somewhat suspect reliability. Many of the prior art systems do not use state-of-the-art circuitry. Power anomalies are sometimes allowed to affect the equipment being supplied power. Many prior art systems are difficult and expensive to repair.